The Study On75000kN Pile Static Loading Test In Dalian Area

With the national economy developing rapidly, the number of super high-rise and long span building structures increase day by day, which put up with high demand of the vertical compressive bearing capacity and the vertical compressive static load test capacity. Researchers in the domestic and overseas all explore the new method to the bearing capacity of single pile. But the static load test can’t be replaced on account of the advantage of high reliability. Take the situation of application of pile foundation in Dalian as example, the characteristic value of vertical compressive bearing capacity of single pile is over20000kN, the number of pile foundation in which the loading value reaches to48000kN increases obviously. The maximum load in the domestic is50000kN, which can’t meet the demands.This paper conducts the study on the large tonnage (7500t) pile foundation construction quality inspection direct at regional area in Dalian. The development of the theory and practice of the static load test of pile foundation and the problem in the big tonnage static load test are introduced in detail, based on which, the purpose and content of this paper are put forward. Then the load transfer mechanism of piles and soil and several common methods are described.Stack method is adopted to conduct the big tonnage static load test of pile foundation. Comprehensively considering all the involving factors, by choosing conventional main beam, and increasing the size of the secondary beam cross-section of the loading system, a set of reasonable and reliable loading system is designed. Then we check the loading system, including the check calculation of the strength and stability of primary and secondary beam, the height of preloading and capsize problem. Based on the loading system above, with taking the two kinds of representative geological conditions as the objects, a2-D finite element model is established by the numerical calculation software ADINA. Through numerical calculation method the settlement and bearing capacity of the foundation are analyzed, and different replacement methods are chose to tackle with the unqualified test site. Finally we verify the derived results with certain theory, and put up with corresponding loading method for different geological conditions.